New Delhi, India (CNN) -- A bomb exploded Saturday at a private hospital in the tourist city of Agra, India, injuring three people.

The bomb went off at Jai Hospital's reception area, said Brij Lal, spokesman for Uttar Pradesh police. The hospital is about 4 kilometers (2.5 miles) from the famed Taj Mahal, India's most popular tourist destination.

The blast blew out window panes and damaged the hospital's waiting room, where the three injured people were, said P.K. Tiwari, the inspector general of police in Agra. One of them sustain burn injuries.

"It is difficult to say what the cause and motive of the blast were. But we know that this was not a sophisticated device and seems to have not created too much impact," Tiwari said. "My guess is this is a crude bomb."
Police at the scene said they spotted several unclaimed lunch boxes and bicycles near the blast site.

India's Home Ministry said it had dispatched commandos to Agra and was in the process of collecting evidence from the scene.

The Agra blast occurred a day after Indian Prime Minister Manmohan Singh warned the nation's senior police officers about India's vulnerability.

"The security environment in the country continues to be uncertain," Singh said in remarks at a police conference Friday. "The recent terrorist attacks in Mumbai and Delhi are grim reminders of the grave challenges posed by terrorism to our national security."

India has suffered a spate of attacks in recent years, including the November 2008 siege of Mumbai that killed 163 people.

This month, a bomb inside a briefcase at the high court in the capital, New Delhi, killed 11 people and injured 74 others.

The Islamic extremist group Harkat-ul-Jihad-al-Islami claimed responsibility for that attack in an e-mail to several TV news channels. Authorities have detained three suspects from the Kashmir region.

In July, 19 people were killed in three deadly blasts in Mumbai, India's largest city and financial hub. No one has been arrested yet.